- Hi Everyone,
In regard to recent discussions on cylindrical map projections, I thought I
would toss a 'tangent' thought into the mix.
Years ago, due to being confused myself, I researched the available
literature for cylindrical map projection formulas. I eventually gave the
notes I made to Gerald Evenden and he greatly expanded on them. Chapter 4 of
his Libproj4 Manual (Mar 2005), in my 'obviously biased' opinion, is the
best reference one can find on cylindrical map projections. Enough said on
that subject!
BTW, daan Strebe I just recently came across your Oct 06 CaGIS Map
Projection article. Thanks for mentioning me!
I've recently recovered enough from medical problems to be able to resume,
as a student, a 'GIS Certificate' course at ODU so that I could learn
'ArcGIS 9.2'. My new Instructor, for some reason, was not amused to learn
that the textbook she chose for the class (ISBN: 0-13-129317-6) features
some of my graphics on page 44. Regretfully, there are at least 4 author
introduced errors on that page alone.
Some graphics:
On the MapHist list-serv in 2005 someone made a comment about a map based on
the phrase 'The World is my Oyster'. I replied with the following comments.
Note that my claim here is that the graphics below are merely visually
interesting, however, for most of them the forward formulas are available.
This one was where I was experimenting with summing the X and Y coordinates
of different graticule groups just to see what developed:
http://www.galleryofmapprojections.com/images/seashell.pdf
Everyone that experiments with map projection formulas comes up with
unexpected, but visually interesting mistakes. Here are some more of my
'amusements':
This one was where I was experimenting with the Nell Modified Conic -- until
I realized that Snyder's description (in Flattening) was incomplete. The
pattern produced in what I had already done just popped out at me, so, I
cleaned the graphic up (lots of grunt work) in Corel Draw and saved it:
http://www.galleryofmapprojections.com/images/Mickey.pdf
Dr. Don Zeigler (Geog Dept, ODU) named this one the Bay Window projection.
It was one of my earliest goofs. Even though I saved the formulas, I don't
remember how I arrived at this one:
http://www.galleryofmapprojections.com/images/baywindow.gif
This one came about because I accidentally put the divide symbol in the
place of the subtract symbol in the X coordinate portion of Moir's formulas.
At that time I had not seen an actual graphic of the projection and John
Snyder was the one who caught my error. He suggested I save the formulas and
name it the 'Bad Times' projection:
http://www.galleryofmapprojections.com/images/badtimes.gif
This Polycylindrical projection came about from experimenting with various Y
coordinate formulas in place of the ones Dr. Tobler used in his paper on
Polycylindricals. I kept it because it was 'visually' interesting.
http://www.galleryofmapprojections.com/images/polycyl.gif
I did not give this one a name. It is amazing in that with one set of
formulas the outer portion of the graticule forms a rectangle while the
parallels within are curved:
http://www.galleryofmapprojections.com/images/Wvplt31.gif
A link to Gerald Evenden's Libproj4 Manual that I mentioned above can be
found at my web site.
Thanks for reading.
Paul B. Anderson FCCS (USN, Retired)
Kingsport, TN native living in Norfolk, VA
http://www.galleryofmapprojections.com